Abstract

The observed polarization of starlight is regarded as being due to absorption by interstellar dust. A mechanism for alignment of the dust grains, due to Davis and Greenstein, is analyzed. A dissipative torque, due to paramagnetic relaxation in the grains, tends to line up a spinning dust grain in the interstellar magnetic field. This aligning torque is opposed by the randomizing effect of collisions with interstellar hydrogen. The aim of this paper is to find the distribution of orientations which results. The analysis is carried out through use of the Fokker-Planck equation. The solution is carried to completion for the case of small magnetic fields and nearly spherical dust grains, and the resulting polarization parameter is found. The spectrum of relaxation times due to the collisions is also found.